CS6403 datasheet(9/54 Pages) CIRRUS

9 / 54 page

OVERVIEW

In hands-free speakerphones, the signal from the

far end may echo about the near-end environ-

ment and then be received at the near-end

microphone.

When heard at the far end, this

echo signal can be very annoying, particularly if

the signal is delayed by transmission or signal-

processing delays.

Voice switching is a particularly simple tech-

nique for eliminating this echo, but since it

imposes half-duplex communication, it seriously

compromises conversation quality.

Echo cancellation can provide high-quality, full-

duplex communication, but typically must be

implemented using expensive digital signal-proc-

essing hardware.

Echo Cancellation in the CS6403

The CS6403 provides high-quality echo cancel-

lation at low cost.

This breakthrough in

cost/performance is made possible on the

CS6403 by custom, application-optimized proc-

essing blocks, which are integrated on a single

die, as shown in Figure 2.

One of these processing blocks is the AFP

(Adaptive Filter Processor).

This block imple-

me nts a 5 1 2 -ta p A F IR ( Ad aptive Finite

Impulse-Response) filter which is updated using

an enhanced least-mean squared (LMS) algo-

rithm. At a sampling rate of 8 kHz, it can cancel

up to 64 ms of echo. By default, 10 ms of the

available 64 ms are allocated to a network can-

celler (NEC), and the remaining 54 ms are

allocated to an acoustic echo canceller (AEC).

RESET

CLKIN CLKOUT

DVDD0

PLL/Oscillator

SSI

CPU

AFP

CODEC

SCLK

SFRAME

SMASTER

SDO

SDI

RESERVED0

DGND0

RESERVED1

GPIN3

CONFIG

GPIN0

GPIN1

GPIN2

SCLK_RATE0 SCLK_RATE1

DVDD1

DGND1

PVDD

PGND0

PGND1

AVDD

SPKROUTP

SPKROUTN

VREF

VCM

MICIN

AGND0

AGND1

GPOUT0

GPOUT1

RESERVED2

RESERVED3

RESERVED4

SSYNC

SYNCOUT

UALAW

RESERVED5

RESERVED6

CLK_SEL

Figure 2. CS6403 Internal Block Diagram

CS6403

DS192PP6

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